Synthesis and Characterization of New Square Planar Iridium

May 5, 1994 - Cynthia A. Miller, Thomas S. Janik, Charles H. Lake, Laurence M. Toomey,. Melvyn Rowen Churchill,* and Jim D. Atwood*. Department of ...
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Organometallics 1994, 13, 5080-5087

5080

Synthesis and Characterization of New Square Planar Iridium Complexes [truns-Ir(CO)La] (L= PCy3, X = OH or OCH3; L = P(p-tolyl)s, X = OCH2CsHs or O(p-C&CH3)): Crystal and Molecular Structures of trans-Ir(C0)(OH)(PCy3)2, truns-Ir(CO)(OCH&Hs) (P(p-tolyl)3)2, and truns-Ir(co)(O-p-C6&CH3) (P(p-tolyl)& Cynthia A. Miller, Thomas S. Janik, Charles H. Lake, Laurence M. Toomey, Melvyn Rowen Churchill,* and Jim D. Atwood* Department of Chemistry, University a t Buffalo, State University of New York, Buffalo, New York 14260-3000 Received May 5, 1994@ Three new Ir(1) complexes have been prepared, characterized and studied by X-ray crystallography, No evidence is found for pi-donation from a n alkoxy ( I ~ ( C O ) ( ~ C H Z C ~ H ~ ) ( P ( ~ to iridium. The phenylmethoxy t ~ l y l ) ~or) ~a )n aryloxy (Ir(Co)(o-p-CsH4CH3)(P(p-tolyl)3)~) crystallizes in the triclinic space group Pi with a = complex Ir(Co)(oCHzC6Hs)(P(p-tolyl)3)~ 10.5187(16), b = 12.8320(15), c = 17.4940(19)81, a = 71.447(8), /3 = 84.907(11), y = 72.407(ll)’,V = 2133.8(5)A3 and 2 = 2. The structure was solved and refined to R = 2.48% for 4567 reflections with F, > 6a(F0). Interatomic distances of note are Ir-P = 2.306(2) and 2.334(2), Ir-CO = 1.806(6) and Ir-0 = 2.022(4)A. The p-cresolate derivative crystallizes as the p-cresol adduct I ~ ( C O ) ( O C ~ C H ~ ) ( P ( ~ - ~in~the ~ ~monoclinic ) ~ ) Z ~space H ~group ~ ~ ~ ~ H P21h with a = 21.1172(28), b = 12.0167(15), c = 22.5658(31)& /3 = 117.180(10)’, V = 5094.0(12)A3 and 2 = 4. The structure was refined to R = 4.26% for 3296 reflections with F, > 60(F0). Interatomic distances include Ir-P = 2.322(4) and 2.330(4), Ir-CO = 1.781(13) and Ir-0 = 2.067(7)81. The hydroxy derivative Ir(CO)(OH)(PCy& crystallizes in the triclinic space group Pi with u = 9.916(3), b = 10.305(4), c = 10.825(4)A, a = 114.16(3),’/3= 109.55(3), y = 90.14(3)’, V = 938.6(5)A3and 2 = 1. This structure is disordered with a scrambled image of the carbonyl and hydroxide ligands. Distances of note are Ir-P = 2.331(1), Ir-CO = 1.887(13) and Ir-OH = 1.978(12)& the Ir-CO and Ir-OH distances may suffer from systematic errors due to disorder. Four-coordinate, 16-electronYsquare-planar Id11 complexes are very important in the study of organometallic chemistry. Vaska’s complex1 and analogues have open coordination sites and have been known to undergo reactions such as oxidative addition,, ligand substitution,, simple adduct formation4 and i n ~ e r t i o n .Syn~ thesis of these complexes has traditionally been accomplished by reduction of a n Ir(II1) salt a t elevated temperature in the presence of a phosphine ligand and a reducing agent:’ IrC13*4H,0

N,N-DMF + PR, trans-Ir(CO)(C1)(PR3),

(1) Another, recently published route, by Burk and Crabtree occurs at room temperature+ [Ir(cod)Cl],

PRS

co

Ir(cod)(Cl)(PR,), tr~ns-1r(CO)(Cl)(PR,)~ (2)

Vaska’s-type alkoxy and aryloxy complexes have been formed by a simple metathesis reaction in which the Abstract published in Advance ACS Abstracts, November 1,1994. (l)Vaska, L.;Peone, J., Inorg. Synth. 1974, 15, 64.

@

chloro complex reacts with a sodium alkoxide forming the desired product and NaCl?*

+

-

trans-Ir(CO)(Cl)(PR,), NaOR trans-Ir(CO)(PR,),OR’

+ NaCl

(3)

This route has proven to be successful in the formation of R=p-tolyl; R’=CHzC& or p-CeH4CH3 in this work. X-ray crystallography, lH and 31PNMR,IR and elemental analysis of these complexes are reported. Another successful route in the formation of Vaska’stype complexes with varying phosphine ligands is a phosphine ligand exchange reaction, illustrated in reaction 4 for preparation of the hydroxy and methoxy complexes with tricyclohexylphosphine. This route is successful when PR’3 is more electron-rich than PR3. (2) (a) Luo,X.; Michos, D.; Crabtree, R.; Hall, M., Inorg. Chim. Acta 1992,198,429. (b) Cotton, F. A. and Wilkinson, G., Advanced Inorganic Chemistry, Fifth Ed.;John Wiley and Sons: New York (1988). (c) Zhou, P.; Vitale, A. A.; San Filippo, J.; Saunders, W. H., J . Am. Chem. SOC. 1985,107, 8049. (3) Bernard, K. A.; Atwood, J. D. Organometallics 1987, 6 , 1133. (4)(a) Rees, W. M.; Churchill, M. R.; Li, Y. J.; Atwood, J. D. Organometallics 1988, 4 , 1162. (b) Vaska, L.,Acc. Chem. Res. 1968, 335. (c) Vaska, k;Bath, S., J . Am. Chem. SOC.1966, 88, 1333. (5) (a) Rees, W. M.; Churchill, M. R.; Fettinger, J. C.; Atwood, J. D. Organometallics 1985, 4 , 2179. (b) Rees, W. M.; Atwood, J. D. Organometallics 1988, 4 , 402. (6) Burk, M.; Crabtree, R., Inorg. Chem. 1986,25, 931.

0276-7333/94/2313-5080$04.50/00 1994 American Chemical Society

Organometallics, Vol. 13, No. 12, 1994 5081

Square P l a n a r Iridium Complexes

trans-Ir(CO)(PR,)&

+ ZPR, -

truns-Ir(CO)(PR,)&

+ 2PR3 (4)

Table 1. IR and 31PNMR Data trans Ir(1) complex IR“YCO (cm-l) 31PNMRb (ppm)

R = p-tolyl; R = Cy; X = OH or OCH, Whether pi-donation from an alkoxo (or aryloxo) ligand to a late transition metal is significant remains a question. Based on relative stabilities of late-transition metal-X bonds (X = oxygen-, nitrogen- or carbondonor ligands), Bryndza and Tam concluded that no significant pi interaction exists for bonds of alkyl, alkoxo or amido ligands to late-transition metal ~ e n t e r s . ~ Caulton Using structural data8 and YCO frequen~ies,~ and coworkers have concluded that extensive pi-donation exists for Ir-OCH2CF3 and for Ru-OCH2CF3. To provide further data on the nature of late-transition metal-oxygen-donor ligand bonds we have prepared new alkoxo and hydroxo complexes and examined the structures of three complexes.

Experimental Section Materials. IrC13.3H20 was purchased or borrowed from Johnson Matthey. Tri-p-tolylphosphine and tricyclohexylphosphine were purchased from Strem Chemical Company. These materials were used as received without further purification. Solvents. Benzene and THF were refluxed in a Nz atmosphere over Nahenzophenone until the solution became blue or purple. Cyclohexane was refluxed in a Nz atmosphere with finely divided CaHz overnight. The solvent was then distilled into a collection flask which had been evacuated three times with subsequent Nz backfilling. The purified solvents were stored in a n inert atmosphere glove box. Benzyl alcohol, p-cresol, and CDzClz were stirred overnight with finely divided CaH2, followed by vacuum distillation. CDzCl2 was distilled into an oven-dried pressure-tube fitted with a Teflon stopcock. The purified solvent was stored in an inert atmosphere glovebox. Dry benzyl alcohol and p-cresol were stirred with Na overnight followed by removal of excess solvent forming the sodium alkoxide salts. The solvents were purchased from Aldrich Co. except CDzClz which was purchased from Cambridge Isostope Labs. Instrumental Measurements. IH and 31PNMR spectra were recorded on a Varian VXR-400. References were set to residual solvent peaks in the IH NMR spectra. 31P NMR spectra were referenced to a n external sample of H3P04 at 0.0 ppm and are proton decoupled. All chemical shifts are reported in ppm and all coupling constants (J)are reported in Hz. Infrared spectra were obtained using a Mattson Polaris Fourier transform spectrometer as KBr disks. Elemental Analysis was done at E & R Microanalytical. Preparations. All syntheses were accomplished under a n argon or nitrogen atmosphere (unless otherwise noted) using an argon filled glovebox, Schlenk or high vacuum techniques. Square planar iridium complexes, trans-Ir(COXCl)(P(p-tolyl)3)2, trans-Ir(CO)(OH)(P(p-tolyl)3)2 and trans-Ir(CO)(OCH3)(P(ptolyl)& were prepared as previously described.1° General Preparation of Ir(CO)(P(p-tolyl).&X(X = OCH2CA or O-p-C&C&). A solution of trans-Ir(CO)(Cl)(P(p-tolyl)& (0.887 g, 1.027 mmol) and NaOR (0.906 g, 6.97 mmol) in THF (50 mL) is stirred under Ar in a sealed flask ~~

~

(7) Bryndza, H. E.; Tam, W., Chem. Rev. l986,88, 1163. (8)(a)Johnson, T. J.; Huffman, J. C.; Caulton, K. G., J.Am. Chem. Soc. 1992,124,2725. (b)Lunder, D. M.; Lobkovsky, E. B.; Streib, W. E.; Caulton, K. G., J.Am. Chem. SOC.1991, 113, 1837. (9)Poulton, J. T.; Folting, K.; Strieb, W. E.; Caulton, K. G., Inorg. Chem. 1992,31, 3190. (10)(a) Randall, S. L.; Thompson, J. S.; Buttrey, L. A.; Ziller, J. W.; Churchill, M. R.; Atwood, J. D., Organometallics 1991, 10, 683. (b) Lawson, H. J.;Atwood, J. D., J. Am. Chem. Soc. 1989,111,6223.

*HNMR (ppm) in CD2Cl2

trans Ir(1) complex

2.3-1.2 (multiple peaks), -l.O(t)J=7.5Hz WCO)(OCHs)(PCys)z 2.3-1.2 (multiple peaks), 3.5 (s) ~(CO)(OCHZCSHS)(P(~-~O~Y~)~)~ 7.8-6.4 (multiple peaks), 4.2 [s, lH], 2.4 [s, 10 HI Ir(CO)(OC&CH3)(P(p-tolyl)3)~ 7.8-6.4 (multiple peaks), 2.6 [s, 2H], 2.3 [s, 9.5 HI

WO)OH(PCys)z

Table 3. Elemental Analyses actual % (calculated %) trans Ir(1) complex

Ir

Ir(CO)(OCHzC&)(P(p-t0lyl)3)2 20.2 (21.2) I~(CO)(OC&CH~)(P(P-~OI~~)~)Z 20.7 (21.2) WCO)(OH)(PCY~~ 23.8 (24.1)

C

H

64.0 (66.4) 64.4 (66.4) 55.8 (55.7)

5.2 (5.5) 5.1 (5.5) 8.4 (8.5)

overnight. The THF is removed from the cloudy yellow solution, followed by addition of cyclohexane (40 mL). The solution is stirred and a white solid containing excess NaOR and NaCl is filtered off. The cyclohexane is removed from the filtrate and the product is extracted with benzene (30 mL) followed by filtration of more white solid. The benzene is removed and the remaining solid is recrystallized in a saturated benzene solution layered with hexanes. After 18 h, yellow crystals formed (0.595 g, 0.636 mmol). IR, NMR and elemental analysis data are included in Tables 1-3. General Preparation of trans-Ir(CO)(PCy&X(X = O c a or OH). A solution of trans-Ir(CO)(P(p-tolyl)3)1X(1.005 g, 1.188 mmol) and PCy3 (1.668 g, 5.95 mmol) in benzene (40 mL) is stirred under Ar in a sealed flask overnight. The benzene is removed and the light yellow product is washed with cyclohexane (20 mL) resulting in a yellow powder (0.643 g, 0.806 mmol, 67.8% yield). Recrystallization is effected with a saturated benzene solution (the solution is heated to prepare the saturated solution) layered with hexanes overnight in a sealed flask under an Ar atmosphere. IR and NMR data and elemental analyses are included in Tables 1-3. Collection of X-ray DiffractionData. All three data sets were collected on an upgraded Nicolet‘Siemens P21/R3 difiactometer using molybdenum radiation (%MoKa) = 0.71073A) at ambient temperature (298flK). The experimental method has been described previous1y;ll details are provided in Table 4. All data were merged and corrected for both absorption and for Lorentz and polarization effects. It should be noted that crystals of I~(CO)(OCSH~CH~)(P(~tolyl)&CH3C&OH were of relatively poor quality and yielded a much “weaker” data set than those obtained for the other two species. Solution of Crystal Structures. All calculations were performed under the Siemens SHELXTL-PLUS system12 on a VAXstation 3100 computer. The analytical scattering factors for the neutral were corrected for anomalous d i ~ p e r s i 0 n . I Structures ~~ were solved by a combination of direct methods and difference-Fourier syntheses. Hydrogen (11)Churchill, M. R.; Lashewycz, R. A.; Rotella, F. J., Inorg. Chem. 1977, 16, 265. (12) Sheldrick, G. M., SHELXTL-PLUS, 1990, Siemens Analytical X-Ray Instruments, Madison, Wisconsin, U S A . (13)International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, England, 1974; Volume 4 (a) pp 99-101 (b) pp 149150.

5082 Organometallics, Vol. 13, No. 12, 1994

Miller et al.

Table 4. Details of X-ray Structural Analyses WCO)(OH)(PCys)z

~(~~)(~~~z~s~s)(~(p-tO~Y~)~)z

molecular formula fw crystal system space group a,A

b, A c,

A

a, deg

A deg Y,deg

v, A3

Z d(calc'd), g ~ m - ~ crystal size (mm) P ("-9 min/max transmission 20 range, deg index ranges total reflections collected independent reflections R(int), % reflections above 60 no. of variables residual electron density, e-/A3 R (wR) 60 data R (wR) all data

c50%9~2p2 936.0 tn&Ainic P1 (No. 2) 10.5187(16) 12.8320(15) 17.4940(19) 71.47(8) 84.907(11) 72.407(11) 2133.8(5) 2 1.457 0.3 x 0.25 x 0.25 3.227 0.152/0.294 5-45 h, - l l - O ; k , -13-+13; I , -18-+18 606 1 5605 0.83 4567 497 -0.31-+OS8 2.48% (2.73%) 3.50% (3.81%)

atoms of the organic fragments were included in calculated positions with d(C-H) = 0.96A.14 Data on final R-factors and residuals on electron density maps are compiled in Table 4. However, certain aspects of the structural solution of Ir(CO)(OH)(PCy& merit a more detailed discussion. A complete sphere (20 = 4-45"] of data was collected; these data were merged t o a unique set with Rht = 2.81% for 2462 averaged pairs of reflections. The molecule crystallizes in space group P1 with 2 = 1 and must be disordered, since the ensemble is required t o have a n inversion center. In fact, there are two possible orientations for each entire molecule. The individual molecules pack, in a random fashion, such that their PCys ligands appear to overlap precisely, while carbonyl and hydroxide ligands are observed as overlapping images at the other two coordination sites (see Figure la). We endeavored to refine appropriate atoms of the carbonyl ligand (C(1) and O(1)) and of the hydroxide ligand (O(2)) independently. Much to our surprise, this appears t o have been successful, even though the separation of C(1) and O(2A) (or C(1A) and O(2)) is only 0.441(14&. We also identified a feature near O(2) which could be the hydrogen atom of the hydroxide ligand, defined as H(3) (see Figure lb). This attribution is not entirely secure; we note that the presumed location is associated with an 0(2)-H(3)distance of 1.08A and an Ir(1)-0(2)-H(3)angle of 161". Final atomic coordinates for the three structures are collected in Tables 5-7.

Description of the Molecular Structures

(A)1r(CO)(OCH2CsH~NP(p-tolyl)& This species crystallizes as discrete molecular units. The scheme for labelling atoms is shown in Figure 2. Important interatomic distances and angles are collected in Table 8. The central d8 iridium(1)atom has a slightly distorted square planar stereochemistry. The cis angles range from P(l)-Ir(l)-O(l)= 83.9(1) through P(2)-Ir(l)-O(l)= 96.4(1)",while trans angles are P(l)-Ir(l)-P(2)= 176.9(1)"and O(l)-Ir(l)-C(9)= 173.8(3)". The two indepen(14)Churchill, M. R., Inorg. Chem. 1973,12, 1213.

CsoH49WzPzC7HsO 1044.2 monoclinic P ~ I /(NO. c 14) 21.1 172(28) 12.0167(15) 22.5658(31) 90.000 117.180(10) 90.000 5094.0(12) 4 1.361 0.2 x 0.17 x 0.1 2.712 0.467/0.600 5-45 h, 0-+22; k, 0-+12; I , -24-+24 7305 6698 2.33 3296 569 -1.05-+0.95 4.26% (4.26%) 10.71% (7.55%)

C37H67WzPz 798.0 tn@inic P1 (No. 2) 9.916(3) 10.305(4) 10.825(4) 114.16(3) 109.55(3) 90.14(3) 938.6(5) 1 1.412 0.3 x 0.3 x 0.2 3.655 0.232/0.372 5-45 h, -l-+10; k, -11-+11; I , -11-+11 4924 2462 2.81 2462 196 -1.21-+1.46 2.40% (2.96%) 2.40% (2.96%)

dent iridium-phosphorus distances are Ir(l)-P(l) = 2.334(2) and Ir(l)-P(2)= 2.306(2)A (average = 2.320A). The iridium-alkoxide linkage is defined by Ir(1)-O(1) = 2.022(4)A and the oxygen atom has a "bent" environment with Ir(l)-O(l)-C(2)= 132.8(4)". The 0(1)-C(2) distance is 1.377(7)Ai.

(B)Ir(CO)(OCsH4CHs)(P(p-tolyl)s)z.CH~CsH40H. The iridium complex here crystallizes with CH3CsH4OH molecules of solvation. The relative position of these two species and the atomic labelling scheme are illustrated in Figure 3. Selected interatomic distances and angles are compiled in Table 9. The d8 iridium(1) atom again has a slightly distorted square planar stereochemistry. It is associated with cis angles ranging from P(2)-Ir(l)-C(l)= 89.7(6) through P(l)-Ir(l)-0(2) = 90.2(3)" and trans angles of P(l)-Ir(1)-P(2)= 174.4(1) and 0(2)-Ir(l)-C(l)= 178.9(5)". The iridium-phosphorus distances are Ir(l)-P(l)= 2.322(4) and Ir(l)-P(2) = 2.330(4)A (average = 2.326A). The iridium- henoxide linkage is given by Ir(l)-0(2) = 2.067(7) and is associated with an Ir(l)-0(2)-C(2)angle of 122.5(7)"and an 0(2)-C(2)bond length of 1.347(14)A. Identification of the molecule of solvation as p-cresol rests upon comparison of bond lengths involving the substituents (C(lS)-O(lS)= 1.372(19)Aas opposed to C(4S)-C(7S) = 1.505(23)& and upon the satisfactory behavior of atoms O(1S) and C(7S) under anisotropic refinement. (As shown in Figure 3, the thermal vibration ellipsoids for these atoms are chemically sensible.) The p-cresol moiety is hydrogen bonded to the oxygen atom of the p-cresolate ligand - see Figure 4. The O(2) ... O(1S)' distance is 2.659(12)A. (C)Ir(CO)(OH)(PCy&. This structure is disordered (see above) in a fashion similar to that observed in such species as Ir(CO)C1(PPh&,15 Ir(CO)(CH3)(PPh3)24a and Ir(CO)C1(PCy3)2.16An illustration of the deconvoluted

w

(15) Churchill, M. R.; Fettinger, J. C.; Buttrey, L. A.; Barkan, M. D.; Thompson, J. S., J. Organomet. Chem. 1988, 340, 257. (16) Churchill, M. R.; Lake, C. H.; Miller, C. A,; Atwood, J. D.J. Chem. Crystallogr. 1994,24, 557.

Square Planar Iridium Complexes

Organometallics, Vol. 13, No. 12, 1994 5083 Table 5. Atomic Coordinates ( x 104) and U(eq) Values x 103) for 1r(CO)(OCH~CaHs)(P(p-tolyl)~)~ /cm

,PI11

1

I

,0111

I

Figure 1. Electron density maps from the X-ray diffraction study of Ir(CO)(OH)(PCy&. (a) Residual electron density due to the disordered COIOH groups. Contours are at 0.2 e-/A3 intervals from 0.0 6.0 e-/A3. Based upon a AF map, phased by all atoms other than those of the carbonyl and hydroxide ligands. (b) Residual electron density showing a possible location for the hydrogen atom of the hydroxide li and. Contours at 0.2 e-lA3 intervals, starting at 0.0 e-lh; orientation as above. Based upon a AF map, phased by all atoms save H(3).

-

X

V

7

1691(1) 2254(1) 1254(1) 1443(5) 2045(6) 1167(6) -58(6) - 1264(7) -2398(7) -2346(8) - 1167(8) -22(7) 1908(7) 2804(5) 1888(6) 2304(6) 364465) 4554(6) 415 l(5) 4069(8) 957(5) 34(5) -966(6) - 1069(6) -135(6) 863(6) -2190(7) 3673(5) 3918(6) 5012(6) 5910(6) 5691(6) 4585(6) 7102(8) 1412(5) 26 12(5) 2796(6) 1818(6) 6416) 429(6) 2016(8) 2344(5) 3393(5) 4297(6) 4180(6) 3128(6) 2235(5) 5226(8) -452(5) -847(5) -2168(6) -3 150(6) -2771(5) -l U ( 5 ) -4588(6)

3332(1) 2533(1) 4092(1) 1784(3) 5526(4) 1303(5) 882(4) 1622(5) 1258(6) 163(6) -569(6) -219(5) 4674(5) 3482(4) 4402(5) 5233(5) 5166(5) 42 19(5) 3373(4) 61 1l(5) 2126(4) 1746(5) 1440(5) 1507(5) 1865(6) 2168(6) 1184(6) 1237(4) 403(5) -550(5) -702(5) 163(6) 1098(5) -1785(7) 5535(4) 5744(5) 6808(5) 7706(5) 7501(5) @41(5) 8874(5) 3307(4) 2348(4) 1811(5) 2196(5) 3137(5) 3696(5) 1648(7) 4229(4) 3752(5) 3847(5) 4426(5) 49 15(5) 4820(5) 4493(7)

2109(1) 1055(1) 3167(1) 2733(2) 102l(3) 3529(3) 3643(3) 3321(4) 3454(4) 3900(4) 4234(4) 4115(4) 1454(3) 157(3) -351(3) -943(3) - 1066(3) -586(3) 20(3) - 1680(4) 682(3) 1223(3) 958(4) 172(4) -356(4) - 108(4) - 103(5) 1316(3) 939(3) 1137(4) 1724(4) 2082(4) 1893(3) 1955(5) 2974(3) 2657(4) 2503(4) 2661(3) 2970(4) 3130(4) 2470(4) 4045(3) 4039(3) 4673(4) 5331(4) 5360(3) 4722(3) 5986(5) 3510(3) 4289(3) 4469(4) 3890(4) 3125(4) 2924(3) 4078(5)

(A2

11ie014

molecule is provided in Figure 5 . Appropriate distances and angles are collected in Table 10. The central iridium(1) atom is associated with cis angles ranging from 89.1(3) through 91.0(3)' and with OEquivalent isotropic U, defined as one-third of the trace of the the trans angles P(l)-Ir(l)-P(lA)= 180.0" (exactly) and orthogonalized Uv tensor. C(l)-Ir(l)-O(2)= 167.2(4)'. The two equivalent iridiumphosphorus distances are Ir(l)-P(l) = Ir(l)-P(lA) = (CO)(OCsHs)(PPh3)2.l8Dimensions for all of these spe2.33Ul)A. The remaining two ligands are associated cies are compared in Table ll. with distances of Ir(l)-C(l) = 1.887(13)A (for the carThe most obvious result is that the alkoxide derivabonyl ligand) and Ir(l)-0(2) = 1.978(12)A (for the is associated tive, Ir(CO)(OCHzCsH5)(P(p-tolyl)3)2 hydroxide ligand). Disorder renders impossible a true with: (1) the shortest Ir-0 distance (2.022(4)81, as assessment of the accuracy (as opposed to precision) of opposed to Ir-O(phenoxide1 distances of 2.049(4)-2.067these two bond lengths. (7)&; (2) the longest 0-C distance (1.377(7)Aas o posed (D) Discussion of the O-Bonded Ligands. The to O-C(aromatic)distances of 1.302(6)-1.347(14) 1; and present study allows a comparison of bond distances and (3)one of the larger Ir-0-C angles (132.8(4)",as opposed other parameters for the structural isomers Ir(C0)to values of 122.5(7)' for the Ir-O-CsH&H3 system and (OCHzCsHs)(P(p-tolyl)3)2(which has an iridium-alkoxide (which has linkage) and Ir(CO)(OC6H4CH3)(P(p-tolyl)3)2 (17)Churchill, M.R.; Fettinger, J. C.; Rees, W. M.; Atwood, J. D., an iridium-phenoxide linkage). Previous studies by our J . Orgummet. Chem. 1986,308,361. research groups have involved the related species Ir(18)Bernard, K. A.; Churchill, M. R.; Janik,T. S.; Atwood, J. D., ( C O ) ( O C ~ H ~ ) ( P P ~I ~ )( Z C,O ~ ") ( O C ~ F S ) ( and P P ~Rh~ ) ~ ~ ~Organometallics 1990, 9, 12.

1

Miller et al.

5084 Organometallics, Vol. 13, No. 12, 1994

Table 7 . Atomic Coordinates (x104)and U(eq) Values Table 6. Atomic Coordinates (x 104) and U(eq) Values (Az x 103) for Ir(CO)(OH)(PCy3)2 x 103) for I~(CO)(OCJ&CHJ)(P(~-~~~~~)J)~'CH~CJ&OH X

Y

Z

-2839( 1) -3 146(2) -2488(2) -4254(5) - 1871(4) -3678(8) - 1777(7) - 1112(8) -1010(9) -1496(11) -2142(9) -2272(7) -1344(10) -3744(6) -4102(7) -4521(7) -4572(8) -4217(7) -3825(7) -4982(10) -3555(7) -3281(8) -3529(8) -4068(8) -4347(7) -4108(7) -4337(8) -2402(6) -2092(6) - 1518(7) - 1245(7) - 1554(9) -2115(8) -633(8) -1544(6) -1 116(7) -41 l(7) -85(7) -509(7) -1217(6) 701(7) -2898(7) -3569(8) -3912(8) -3626(8) -2946(9) -2597(7) -4018(10) -2735(6) -2774(7) -2924(8) -3037(7) -297 1(9) -2806(8) -3262( 10) 808(5) 941(8) 497( 11) 643(13) 1194(11) 1579(9) 1468(8) 1323(11)

8421(1) 9189(3) 7818(3) 907 1(10) 7917(7) 8827(11) 69 12(9) 6704(12) 5667(14) 4879( 15) 5090(12) 6084(11) 3763( 14) 8344(10) 7429( 11) 6766(12) 6968(11) 7889( 11) 8 5 7 310) 6182(14) 10575(10) 11267(11) 12317(13) 12739(11) 12063(13) 10975(11) 13915(11) 9471(9) 8564(11) 8749( 11) 9766(15) 10676(13) 10495(11) 9980(14) 7560(9) 8190(10) 7987( 13) 7 109(14) 6496(12) 6711(11) 6843(14) 6523( 11) 6262( 12) 5344(13) 4621( 12) 487 1(12) 5801(11) 3651(14) 8801(10) 8499(12) 9270( 12) 10366(13) 10679(12) 9924( 11) 11212(15) 10632(9) 9576( 13) 8723( 17) 7661( 19) 7442( 13) 8321(15) 9397(14) 6290(12)

-2165(1) -1387(2) -2952(2) -3235(5) - 1407(4) -2820(8) - 1114(6) -546(7) -245(8) -438(9) -980(9) - 13lO(7) -41(9) -1183(5) -1567(6) - 1384(8) -8 12(8) -424(7) -614(6) -596( 10) - 1637(6) - 1964(6) -2148(7) -2027(7) -1717(7) - 1538(6) -2216(9) -574(6) -137(6) 481(6) 694(7) 268(8) -356(7) 1376(7) -2658(6) -2848(7) -2628(7) -2178(7) - 1994(6) -22 12(6) - 1932(8) -3373(6) -3447(7) -3815(8) -4105(8) -4015(7) -3653(6) -4523( 11) -3635(6) -4236(6) -4735(7) -4650(7) -4033(8) -3534(7) -5204(8) 867(5) 1126(9) 768(10) 1050(12) 1663(11) 2008(9) 1762(8) 1957(11)

Weq),

nEquivalent isotropic U, defined as one-third of the trace of the orthogonalized Uij tensor.

126.5(3)' for the Ir-O-C6& system; only the Ir-O-C6F5 system has a larger value -135.4(3)"). It should be noted that the M-0-C angle for each of the species studied (Table 8) has a value in excess of 120". Thus, while we might expect the oxygen atom to be sp3 hybridized (two bonding pairs of electrons at -105" to each other and two lone pairs of electrons), the M-0-C angles of 122.5(7)-135.4(3)' suggest consid-

X

Y

Z

0 -2008(1) -1438(5) -2236(5) -2559(4) -2869(5) -1943(5) -3351(5) -1657(4) -1006(5) -2892(5) - 1701(6) -507(6) -2359(6) -5149(5) -3687(4) -4906(6) -3653(5) -6393(5) -6354(6) 1162(10) 1913(7) -1297( 10)

0 -29 1(1) 2380(4) 4627(4) 1451(4) 2295(4) 3809(4) 3727(4) - 1115(4) -25 1l(5) - 1313(5) -3099(6) -2960(6) -1735(6) -1097(5) -1287(4) -3561(6) -2887(5) - 1756(6) -3338(6) 810(11) 1010(10) -402( 10)

0 -2038( 1) -2092(5) -651(5) - 1982(4) -592(5) -2017(5) -536(5) -3754(4) -3979(5) -5141(4) -6635(5) -5270(5) -6396(5) -3 170(7) -2227(5) -2460(8) -2639(6) -2980(8) -3352(8) -658( 11) -1140(8) 891(10)

(Az

U(eW

"Equivalent isotropic U, defined as one-third of the trace of the orthogonalized U, tensor.

Table 8. Selected Interatomic Distances (A) and Angles for I~(CO)(OCHZC~HS)(P(~-~~~Y~)~)Z 2.334(2) 2.306(2) Ir( 1)-P( 1) 2.022(4) 1.806(6) Ir( 1)-0( 11 P(l)-C(11) P( 1)-C(3 1) P(2)-C(51) 0(1)-C(2) W)-C(3) C(3)-C(8) C(5)-C(6) CU)-C(8) P( 1)-Ir( 1)-P(2) P(2)-Ir( 1)-O( 1) P(2)-Ir( 1)-C(9) Ir(1)-P(1)-C(l1) C( 11)-P( 1)-C(21) C( 1l)-P(l)-C(31) Ir( i)-P(2)-c(41) C(41)-P(2)-C(5 1) C(41)-P(2)-C(61) Ir(l)-O(l)-C(2) C(2)-C(3)-C(4) C(4)-C(3)-C(8) C(4)-C(5)-C(6) C(6)-C(7)-C(8) Ir( 1)-C(9)-0(9) P(l)-C( 11)-C(16) P( 1)-C(21)-C(26) P(l)-C(31)-C(36) P(Z)-C(41)-C(46) P(2)-C(51)-C(56) P(2)-C(61)-C(66)

1.826(5) 1.827(4) 1.821(5) 1.377(7) 1.516(9) 1.382(7) 1.359(10) 1.385(12) 176.9(1) 96.4(1) 89.6(2) 112.8(2) 104.4(3) 103.8(2) 117.1(2) 100.4(3) 103.5(2) 132.8(4) 120.1(5) 118.1(6) 121.0(6) 120.8(6) 178.6(6) 120.6(3) 123.5(5) 119.3(4) 124.6(4) 122.1(3) 116.3(4)

1.834(7) 1.829(6) 1.816(5) 1.157(8) 1.373(8) 1.384(11) 1.356(10) P( 1)-Ir( 1)-O( 1) P(l)-k(l)-C(9) O(1)-Ir( 1)-C(9) Ir(l)-P( 1)-C(21) Ir(1)-P( 1)-C(31) C(21)-P(l)-C(31) Ir( 1)-P(2)-C(5 1) Ir( l)-P(2)-C(61) C(51)-P(2)-C(61) O( 1)-C(2)-C(3) C(Z)-C(3)-C(8) C(3)-C(4)-C(5) C(5)-C(6)-C(7) C(3)-C(8)-C(7) P(l)-C(ll)-C(12) P( l)-C(21)-C(22) P(l)-C(31)-C(32) P(2)-C(41)-C(42) P(2)-C(51)-C(52) P(2)-C(61)-C(62)

83.9(1) 90.2(2) 173.8(3) 117.4(2) 111.9(2) 105.4(3) 115.7(2) 111.3(2) 107.5(2) 113.4(5) 121.6(5) 120.4(5) 119.1(8) 120.5(5) 120.6(4) 118.4(5) 122.9(4) 118.2(4) 120.5(4) 126.1(4)

erably more s-character in the 0-M and 0 - C o-bonds. The key question is whether this indicates the presence of pi-donation from the ligand to the metal.lg A number of alkoxo and aryloxo complexes of iridium have been prepared and structurally characterized. The two parameters most affected by possible pi-donation are the Ir-OR bond distance and the Ir-0-C bond angle. A complete lack of correlation of M - 0 bond distances and M-0-C angles was noted for niobium(V1 and tan(19)Caulton, K. G., New J. Chem. 1994, 18, 25 and references therein.

Square Planar Iridium Complexes

Organometallics, Vol. 13, No. 12, 1994 5085

0

0

Figure 4. Packing diagram for Ir(CO)(OC6H4CH3)(P( ptolyl)3)&&C6H40H, showing hydrogen bonding between the phenolic oxygen atoms of the p-cresol molecule and the p-cresolate ligand.

talum(V) complexes.20 The Ir-0 bond length is affected by a number of factors. Although one might expect Ir(111)-0bond distances to be shorter than Ir(U-0 bond distances (due to the decreasing radius for iridium), the Ir(II1)-0 bonds are typically longer than Ir(I)-O bonds (see Table 11). While this could be attributed to change in the nature of the Ir-0 bond, it could also result from (20)Steffey, B. D.; Fanwick, P. E.; Rothwell, I. P., Polyhedron 1990, 9, 963.

the larger coordination number of Ir(II1) and enhanced steric interactions. The Ir-OCHzCF3 bond distance of 2.169(7$ for Ir(CO)(H)2(0CH2CF3)(PCy3)2was suggested as a typical, non pi-bonded Ir-0 distance.8b However, this is the longest of the well-characterized Ir-OR distances and may well not be typical. The two PCy3 groups may be exerting a steric influence causing this Ir-0 bond to be unusually long. The Ir-OMe bond length of 2.057(8)81 for Ir(CO)(OMe)(TCNE)(PPh3h (TCNE = tetracyanoethylene)may be a more typical IrOMe bond length, especially for Ir(I).21 As an 18ecomplex, pi donation should not be significant. The Ir(I)-ORbonds reported in this manuscript (except for the hydroxide complex) are not significantly shorter than this Ir-0 distance. (21) Janik, T. S.;Bernard, K. A.; Churchill, M. R.; Atwood, J. D., J. Organomet. Chem. 1987,323,247.

5086 Organometallics, Vol. 13, No. 12, 1994

Miller et al.

Table 9. Selected Interatomic Distances (A) and Angles (deg) for Ir(CO)(OC~CH3)(P(p-tolyl)3)z~CH~C&OH (A) Selected Distances in the Iridium Complex k(1)-P(2) Ir(l)-P(l) 2.322(4) Ir( 1)-0(2) 2.067(7) Ir(1)-C(l) P(1)-C(11) 1.837(14) P(l)-C(21) P(l)-C(31) 1.821(10) P(2)-C(41) P(2)-C(51) 1.823(13) P(2)-C(61) 0(1)-C(1) 1.183(16) 0(2)-C(2) c(2)-c(3) 1.425(16) c(2)-c(7) C(3)-C(4) 1.388(22) C(4)-C(5) C(5)-C(6) 1.378(21) C(5)-C(8) C(6)-C(7) 1.366(20)

(B) Selected Angles in the Iridium Complex P(l)-Ir(l)-P(2) 174.4(1) P(l)-Ir(l)-0(2) P(2)-Ir( 1)-O(2) 90.1(3) P(1)-Ir(l)-C(l) 89.7(6) 0(2)-Ir(l)-C(l) P(2)-Ir( 1)-C( 1) Ir(1)-P(1)-C(l1) 115.6(4) Ir(l)-P(l)-C(21) C(ll)-P(l)-C(21) 107.2(6) Ir(l)-P(l)-C(31) C(ll)-P(l)-C(31) 103.0(6) C(21)-P(l)-C(31) Ir(l)-P(2)-C(41) 116.9(5) Ir(l)-P(2)-C(51) C(41)-P(2)-C(51) 103.0(6) Ir(l)-P(2)-C(61) C(41)-P(2)-C(61) 105.2(6) C(51)-P(2)-C(61) Ir(1)-0(2)-C(2) 122.5(7) Ir(1)-C(1)-O(1) 0(2)-C(2)-C(3) 117.6(11) 0(2)-C(2)-C(7) C(3)-C(2)-C(7) 117.2(11) C(2)-C(3)-C(4) C(3)-C(4)-C(5) 124.1(13) C(4)-C(5)-C(6) C(4)-C(S)-C(S) 120.2(14) C(6)-C(5)-C(8) C(5)-C(6)-C(7) 121.0(15) C(2)-C(7)-C(6) P(l)-C(ll)-C(l2) 121.3(11) P(l)-C(ll)-C(16) P(l)-C(21)-C(22) 116.6(11) P(l)-C(2l)-C(26) P(l)-C(31)-C(32) 118.2(8) P(l)-C(31)-C(36) P(2)-C(41)-C(42) 123.7(9) P(2)-C(41)-C(46) P(2)-C(51)-C(52) 118.2(12) P(2)-C(51)-C(56) P(2)-C(61)-C(62) 122.1(10) P(2)-C(61)-C(66)

C63

C13

2.330(4) 1.781(13) 1.842(12) 1.817(12) 1.818(13) 1.347(14) 1.363(18) 1.315(26) 1.562(25)

90.2(3) 90.2(6) 178.9(5) 112.5(5) 115.2(5) 102.1(5) 114.9(6) 112.1(5) 103.2(5) 176.1(17) 125.2(10) 117.8(13) 117.9(16) 121.9(16) 121.9(11) 120.5(9) 125.6(11) 124.7(9) 119.6(11) 124.3(11) 120.2(11)

(C) Distances within the CH3C&OH Molecules of Solvation O(lS)-C(lS) 1.372(19) C(lS)-C(2S) 1.376(24) C( 1S)-C(6S) 1.373(20) C(2S)-C(3S) 1.396(30) C(3S)-C(4S) 1.366(27) C(4S)-C(5S) 1.343(24) C(4S)-C(7S) 1.505(23) C(5S)-C(6S) 1.385(25) (D) Angles within the CH&&OH Molecule of Solvation O(lS)-C(lS)-C(2S) 119.1(13) O(lS)-C(lS)-C(6S) 120.1(14) CQS)-C(lS)-C(6S) 120.5(16) C(lS)-C(2S)-C(3S) 117.6(16) C(2S)-C(3S)-C(4S) 123.1(19) C(3S)-C(4S)-C(5S) 116.5(17) C(3S)-C(4S)-C(7S) 121.4(16) C(5S)-C(4S)-C(7S) 121.9(16) C(4S)-C(SS)-C(6S) 123.7(15) C(lS)-C(6S)-C(5S) 118.2(14)

c45

c44

Figure 5. The deconvoluted structure of Ir(CO)(OH)(PCY3)z. Table 10. Selected Interatomic Distances (A) and Angles (de& for Ir(CO)(OH)(PCy3)z (A) Intramolecular Distances 2.331(1) Ir( 1)-C( 1) 1.978(12) Ir( l)-P( 1A) 1.861(4) P(l)-C(ll) 1.860(5) C(1)-0(1)

W)-P(1) Ir(1)-0(2) P( 1)-C(41) P( 1)-C(61)

1.887(13) 2.33 1(1) 1.854(4) 1.104(16)

(B)"Distances" between Disordered Images C(1)-0(2A) 0(2)-C(W P( 1)-Ir( 1)-C( 1) C(l)-Ir(l)-0(2) C(l)-Ir(l)-P(lA) h(l)-P(l)-C(ll) Ir(l)-P(l)-C(61)

0.441(14) 0.441(14)

0(1)-0(2A) 0(2)-0(1.4)

(C) Intramolecular Angles 89.1(3) P(l)-Ir(l)-0(2) 167.2(4) P(1)-Ir(1)-P(1A) 91.0(3) 0(2)-Ir(l)-P(lA) 112.9(1) Ir(l)-P(l)-C(41) 113.8(2) Ir(l)-C(l)-O(l)

1.041(16) 1.041(16) 90.1(3) 180.0 89.9(3) 112.9(1) 165.6(10)

An expansion of the Ir-0-R angle could also indicate pi donation from the ligand to the metal. As discussed above, any angle '105" indicates some distortion. For Table 11. Geometry of the M-0-C or M-0-H Frameworks a Ru-OCHzCF3 complex an angle of 124.6A was atin Iridium Complexes tributed to pi donation.8a The complexes reported in this manuscript, trans-Ir(CO)(OCH~CsHs)(P(p-tolyl)3)~ M-0 (A) M-0-C(deg) reference and trans-Ir(CO)(OC~H4Me)(P(p-tolyl)3)2 have Ir-0-R 1.978(12) this work angles of 132.8(4)"and 122.5(7)",respectively. These 2.022(4) this work 132.8(4) 2.049(4) 5a 126.5(3) could be considered indicative of pi donation. However, 2.067(7) this work 122.5(7) one of the largest Ir-0-C angles (137")was observed for 2.058(3) 17 135.4(3) Ir(CO)(OMe)(TCNE)(PPh3)z which should not be a pi2.044(2) 18 125.5(2) donor to the iridium.21 Examining all of the Ir-0-C 2.032(10) 138.0(11) 8b 2.169(7) 118.4(7) angles show a range from 118-138" with no clearly 8a 2.057(8) 137.4(9) 19 interpretable pattern. It is most likely that this angle 2.1 18(8) 119.4(9) 20 is controlled by a combination of steric, electronic and packing effects. or aryloxide to the metal is important to the Ir-OR bond. Carbonyl stretching frequencies were also used to Cowan and Trogler also concluded that z-donation from indicate pi d ~ n a t i o n .For ~ a number of trans-Ir(C0)an alkoxide should not be important.22 We do note, (P(p-tolyl)&X complexes (Table 12) prepared in our however, that the Ir-OH bond for the most electron-rich laboratory there are small changes in VCO. Larger shifts iridium center and the most sterically hindered of the are seen for complexes involving alkyl groups where pi Ir(1) complexes, Ir(CO)(OH)(PCy3)2,appears to be subdonation is not possible. We can see no good way to stantially shorter than the Ir-alkoxide linkages; howdifferentiate 0- and n-effects on VCO. For the trans-Ir(CO)(OR)Lz complexes we find no convincing evidence that pi donation from the alkoxide (22) Cowan, R. L.; Trogler, W. C., J.Am. Chem. SOC.1989,111,4750.

Square Planar Iridium Complexes

Organometallics, Vol. 13, No. 12, 1994 5087

Table 12. Carbonyl Stretching Frequencies (KBr) for trans-Ir(CO)X(P(p-tl)~)~ Complex@ X YCO (cm-9 X vco (cm-9 I Br OC@S c1 0CHzCd-k

1967 1966 1962 1957 1953

~sH4CH3 WsHs WH3 CH3 OH

1949 1948 1940 1937 1932

All prepared and characterized in our laboratory.

ever, we stress that disorder renders both this bond length and its esd unreliable.

Acknowledgment. Upgrading the diffi-actometer was made possible by Grant 89-13733from the Chemical Instrumentation Program of the National Science Foundation. JDA acknowledges the National Science Foundation (CHE-9015897) for partial support of this research. Supplementary Material Available: Complete listings of interatomic distances, bond angles, anisotropic thermal parameters, and calculated positions for hydrogen atoms for the three structural studies (15pages). Ordering information is given on any current masthead page.

OM940349T